So in the first example, I am putting CoS 0,1,2,3 in Queue 1 and Queue 1 has a buffer allocation of the port of 80%.

The the second, CoS 0 and 1 go into Queue 1 with a buffer allocation of 30% of the port.

Now, if I run enable QoS on a large scale network, one would assume, this would be a major concern, or, if Queue 1 reaches it threshold of 30%, does it just tail drop or would it use buffers from queue 2?

Re: Enabling QoS on a Switch - Do I lose Bandwidth Capacity?

Ken,

If the port is not over subscribed all traffic will go. If you have 80mb of traffic egressing a 100mb port it won't matter that 60mb is Q1 COS 0 which is only allocated 30%. If you have 150mb/s of traffic your mapping is going to determine what COS traffic will be dropped.

Re: Enabling QoS on a Switch - Do I lose Bandwidth Capacity?

Hey fella :)

Again Thx. So let me make sure I got this right and am really sorry if I am being a dummy.

If i config the port txq-ratio using the command

set qos txq-ratio 2q2t 30 70

If i send 60 Mb of CoS 0 (no other traffic), it will all get sent? Also if I sent 90Mb it would get sent. If I send 110Mb 10Mb has to get dropped and that would use the drop threshold or would wrr determined the dropping of packets.

Or, are we saying from the document you sent, all 6500 ports use weighted tail drop as standard before any other congestion mechanisms take place? (The Catalyst 6000 has implemented an advanced version of tail drop congestion avoidance that drops all packets with a certain CoS when a certain percentage of buffer filling is reached. )

Re: Enabling QoS on a Switch - Do I lose Bandwidth Capacity?

Question
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
Im studying the 100-105 book by Odom and am currently on the topic of Port security. I purchased a used 2960 and I'm trying to follow a...
view more

Symptoms
While deploying a number of 18xx/2802/3802 model access points (APs), which run AP-COS as their operating platform. It can be observed on some occasions that while many of their access points were able to join the fabric WLC withou...
view more

I am going to design and build an LAN network under a tunnel underground with long distance between the switches.
I will have 2 Catalyst switches and 8 Industrial IE3000, and they will be connected with fiber.
For now I am planning on use Layer-2 s...
view more